WO2009145031A1

WO2009145031A1 - Process for producing colloidal crystal and colloidal crystal

Info

Publication number: WO2009145031A1
Application number: PCT/JP2009/058500
Authority: WO
Inventors: 山中　淳平; 真里子篠原; 彰子豊玉; 幸樹吉沢; 佐智子恩田; 米勢　政勝; 内田　文生
Original assignee: 公立大学法人名古屋市立大学; 富士化学株式会社
Priority date: 2008-05-28
Filing date: 2009-04-30
Publication date: 2009-12-03
Also published as: KR101232315B1; CN102036747A; EP2295137A1; US20110123803A1; KR20110049747A; EP2295137A4; JPWO2009145031A1; US9017477B2; CN102036747B; EP2295137B1; JP5663752B2

Abstract

Provided is a process for producing colloidal crystals from which a large single crystal reduced in lattice defects and unevenness can be easily produced at low cost without fail. The process for colloidal crystal production comprises: preparing a colloidal polycrystal dispersion in which colloidal crystals precipitate at a given temperature (preparation step); introducing into a vessel the colloidal polycrystal dispersion in the state of containing fine colloidal polycrystals precipitated (introduction step); and dissolving the colloidal polycrystals and then recrystallizing the dissolved polycrystals (recrystallization step). The crystals thus obtained have fewer lattice defects and less unevenness than the original polycrystals.

Description

Method of producing colloidal crystal and colloidal crystal

The present invention belongs to the technical field of colloids, and more particularly, to a method for producing colloidal crystals using a colloidal polycrystal dispersion that crystallizes with temperature change, and colloidal crystals produced using the same.

Colloid is a state in which colloidal particles having a size of several nm to several μm are dispersed in a medium, and has a wide range of industrial applications in the field of paints, medicines and the like.

By choosing appropriate conditions, the colloidal particles are regularly arranged in the colloidal dispersion to form a structure called "colloidal crystals". There are two types of this colloidal crystal. The first is crystals formed under conditions of a particle volume fraction of about 0.5 (concentration = 50% by volume) or more in a colloidal system (hard sphere system) in which there is no special interaction between particles. This is similar to the regular arrangement phenomenon when macroscopic spheres are packed in a limited space. The second is a crystal structure formed by electrostatic interaction acting between particles in a dispersion system of charged colloid particles (charged colloid system). For example, crystals are formed of a colloidal system in which particles made of a polymer (polystyrene, polymethyl methacrylate or the like) having a dissociative group on the surface or silica particles (SiO ₂ ) are dispersed in a polar medium such as water. Since the electrostatic interaction extends over a long distance, crystals can be formed even with a low particle concentration (long distance between particles) and a particle volume fraction of about 0.001.

Colloidal crystals conduct Bragg diffraction of electromagnetic waves in the same manner as ordinary crystals. The diffraction wavelength can be set in the visible light range by selecting the manufacturing conditions (particle concentration and particle size). For this reason, application development to optical elements including photonic materials is currently being actively studied in and outside the country. At present, the mainstream of the optical material manufacturing method is a multilayer thin film method and a lithography method. Either method is excellent in periodic accuracy, but in the former, only one or two-dimensional periodic structure can be obtained. In the three-dimensional crystal structure (opal structure) obtained by the deposition of the fine particles, the uniformity of the interplanar spacing is good when particles having a uniform particle diameter are used. However, the region with good single crystallinity is limited to about 10 cycles, and construction of a macro three-dimensional structure (that is, a large colloidal single crystal) is difficult in the method of depositing fine particles.

Usually, a colloidal crystal is obtained as a polycrystalline body in which microcrystals of about 1 mm square are gathered, but when it is used as an optical element, a single crystal of cm order is often required. In addition, colloidal crystals generally have various lattice defects and inhomogeneities, which may prevent their use as optical elements. From the above, it is required to establish a method of producing a colloidal crystal that is (1) high quality (ie, the absence of lattice defects and nonuniformity as much as possible) and (2) large single crystals can be produced. It is done.

As a method of controlling the formation of colloidal crystals derived from charged colloid systems, charged colloidal polycrystals have been used so far among parallel plates having a gap of about 0.1 mm with respect to ionic polymer latex / water dispersion systems. A method (Non-patent document 1) for obtaining a single crystal by shear orientation of 1 and a method (non-patent document 2) for applying an electric field to perform crystallization have been reported. However, in the former case, these methods require special equipment for shear field application, and in the latter case, the electrode reaction generates impurity ions, which interfere with crystallization, etc. is there. In addition to this, there is a report in which charged colloidal crystals are solidified with polymer gel and the crystal plane distance is controlled using volume change of gel due to temperature change (Non-patent document 3), however, complicated processes are required. Also, generation of crystals from disordered particle arrangement has not been attempted.

The present inventors have also developed a method for producing a colloidal crystal in which a specific ionized substance is allowed to coexist in a charged colloid dispersion system, and a colloidal crystal is formed by temperature change (Patent Document 1). According to this method, colloidal crystals can be produced relatively easily from various charged colloid systems without the need for special equipment or complicated steps. However, in this method, it is difficult to produce large single crystals exceeding 1 cm.

As a method of producing a colloidal crystal capable of obtaining a large single crystal, the present inventors use a silica colloidal particle / water system which crystallizes with an increase in charge number with pH, and a base is diffused from one end of a sample. We have succeeded in manufacturing the world's largest colloidal crystals of columnar crystals that reach several centimeters in length and cubic crystals with sides of about 1 cm by a method (Non-Patent Documents 4 and 2). However, this method has the disadvantage that crystal growth is extremely time-consuming. In addition, spectroscopic measurement revealed that there is global nonuniformity (tilt and fluctuation) in the lattice spacing of the large crystal thus obtained. This seems to be due to the temporal and spatial inhomogeneity of the base concentration essential to the diffusion phenomenon, the diffusion disorder, and the like. Although the heterogeneity of the interplanar spacing decreases with time, a distribution of about 10% exists in the interplanar spacing even if the base concentration becomes almost uniform. For this reason, the application as an optical element is limited.

For this reason, the inventors of the present invention conducted intensive studies to develop a method of producing a colloidal crystal capable of easily and inexpensively producing a large single crystal with little lattice defect and nonuniformity (Patent Document 3). In this method, a colloidal dispersion in which pyridine is added to silica colloid is prepared. Since the degree of dissociation of pyridine changes with temperature, the colloidal dispersion liquid has the property that the charge density of the silica particles increases as the temperature increases, and colloidal crystals are precipitated. The colloidal dispersion is placed in a container without colloidal crystals deposited. Then, one end side of the container is warmed and set to a temperature at which the colloidal crystal is locally deposited. Further, the range set to the temperature at which the colloidal crystal precipitates is gradually expanded to grow the colloidal crystal. The colloidal crystal thus obtained was an extremely large single crystal, and was also reduced in lattice defects and inhomogeneities. For this reason, the half value width in an absorption spectrum and a reflection spectrum could be set in a very narrow range of 20 nm or less. In addition, the spatial non-uniformity of the diffraction wavelength can be made extremely high, of 2.0% or less. Here, spatial nonuniformity refers to the standard deviation of the spatial distribution of diffraction wavelengths of a colloidal crystal measured by reflection spectroscopy or transmission spectroscopy, divided by the weighted average value of diffraction wavelengths, and expressed as a percentage (Same below).
B. J. Ackerson and N. A. Clark, Phys. Rev. A 30, 906, (1984) T. Palberg, W. Moench, J. Schwarz and P. Leiderer, J. Chem. Phys. 102, 5082, (1995) J. M. Weissman, H. B. Sunkara, A. S. Tse and S. A. Asher, Science, 274, 959, (1996) N. Wakabayashi, J. Yamanaka, M. Murai, K. Ito, T. Sawada, and M. Yonese Langmuir, 22, 7936-7941, (2006) JP-A-11-319539 Unexamined-Japanese-Patent No. 2004-89996 JP, 2008-93654, A

In the method of producing a colloidal crystal described in Patent Document 3, the temperature at which the colloidal crystal precipitates from the colloidal dispersion changes not only by the concentration of pyridine but also by a slight ionic impurity. In order to precipitate out, there has been a problem that it is necessary to pay close attention to the purity of chemicals and solvents, cleaning of containers and the like. The present invention has been made in view of such conventional circumstances, and is a method for producing a colloidal crystal which can easily, inexpensively and reliably produce a large-size colloidal crystal with few lattice defects and nonuniformities. Providing is an issue to be solved.

In the method for producing a colloidal crystal according to the present invention, a preparation step of preparing a colloidal polycrystal dispersion liquid in which colloidal polycrystals melt at a predetermined temperature, a storage step of containing the colloid polycrystal dispersion liquid in a container, and the inside of the container Recrystallization process of recrystallizing the colloidal polycrystal by changing the temperature of a part or all of the region of the colloidal polycrystal dispersion of the above to a temperature at which the colloidal crystal is precipitated again And.

In the method for producing a colloidal crystal of the present invention, first, in the preparation step, a colloidal polycrystal dispersion in which the colloidal polycrystal melts at a predetermined temperature is prepared. Then, in the storing step, the colloidal polycrystal dispersion in which colloidal polycrystals are deposited is housed in a container. Furthermore, in the recrystallization step, the temperature of a partial region or the entire region of the colloidal polycrystal dispersion in the container is set to a temperature at which the colloidal crystal does not precipitate, and then changed again to the temperature at which the colloidal crystal precipitates. That is, since the colloidal polycrystal dispersion liquid in which the colloidal polycrystal has been precipitated in advance is used for recrystallization after melting, recrystallization can be surely performed. For this reason, it is possible to precipitate colloidal crystals with good reproducibility without paying great attention to the purity of chemicals and solvents, cleaning of containers, and the like. Moreover, according to the test results of the inventors, the colloidal crystal thus obtained becomes a very large single crystal, and also has few lattice defects and nonuniformities.

Therefore, according to the method for producing a colloidal crystal of the present invention, it is possible to easily and inexpensively produce a large-size, colloidal crystal with few lattice defects and nonuniformities, and reliably.

In the method for producing a colloidal crystal of the present invention, in the recrystallization step, a temperature control means sets a part of the colloidal polycrystal dispersion to a temperature at which the colloidal crystal melts to form a melting region and move the melting region. It can be recrystallized by the zone melt method. According to this method, large colloidal single crystals can be easily produced. In addition, when the impurity colloidal particles are present in the colloidal polycrystal dispersion, it also has the effect of preventing the impurity colloidal particles from entering the colloidal single crystal.

Here, the movement of the melting region can be performed by the movement means which enables relative movement between the temperature control means and the container. If the movement of the melting region is performed in this way, the relative movement velocity of the melting region is slowed to slow recrystallization from the molten state to the crystalline state to achieve enlargement of the single crystal, or the relative movement velocity of the melting region. The recrystallization can be easily controlled by making the single crystal faster and making the single crystal faster. For this reason, it is possible to balance the quality of the colloidal crystal and the efficiency of production according to the purpose.
The movement of the melting region may be performed by moving the container, may be performed by moving the temperature control means, or may be performed by moving both the container and the temperature control means. .
The moving speed of the melting region may be appropriately selected depending on the composition of the colloidal polycrystal dispersion, the temperature of the melting region, etc., but usually 10 mm / min or less is preferable, and 2 mm / min or less is more preferable. If the moving speed of the melting region is too fast, it becomes difficult to precipitate large colloidal single crystals.

In addition, in the storage step, the colloidal polycrystal dispersion is preferably filled between two walls facing in a substantially parallel manner. In this case, free convection in the container hardly occurs, so that the growth of the colloidal crystal is not easily disturbed, and a large single crystal with less lattice defects and nonuniformities can be manufactured. In this case, the direction of changing the temperature of the colloidal dispersion may be either parallel to the wall or perpendicular to the wall. In addition, even when a highly viscous liquid such as ethylene glycol or glycerin is used as the colloid dispersion medium, the same effect can be obtained because convection hardly occurs.

As a method for preparing a colloidal polycrystal dispersion in which colloidal polycrystals melt at a predetermined temperature, it is possible to add a weak acid or a weak base whose degree of dissociation changes with temperature change. For example, the degree of dissociation of pyridine, which is a weak base, increases with increasing temperature (pK _b values in salt-free aqueous solution of pyridine determined by electrical conductivity measurement are 9.28 and 8.53 at 10 and 50 ° C. Decreased linearly with the temperature). Therefore, when pyridine is allowed to coexist in a colloidal dispersion system such as a silica colloidal dispersion system, it is considered that the effective surface charge density σ _e value of the colloidal particles increases with the temperature rise. Moreover, the above dissociation at various temperatures is in equilibrium in a much shorter time than the time required for the temperature change of the system under normal use conditions. That is, since the σ _e value is uniquely determined by the sample temperature and is not dependent on the temperature history and the like up to that point, melting and recrystallization of the colloidal polycrystal dispersion occur thermoreversibly.

Hereinafter, weak bases, weak acids and salts whose degree of dissociation changes with temperature change are exemplified, but not limited thereto. Preferred weak bases include, for example, pyridine and pyridine derivatives (monomethylpyridine, dimethylpyridine, trimethylpyridine etc.), which increase in degree of dissociation with increasing temperature. These pyridines or pyridine derivatives are particularly preferred for use in the present invention because they have a suitable pK _b value for the crystallization of the silica particles and that the change in the pK _b value with temperature is sufficiently large. Other than this, uracil, quinoline, toluidine, aniline (and derivatives thereof) and the like can be used as a weak base, and the degree of dissociation also increases with the temperature rise.

On the other hand, examples of weak acids include acids whose degree of dissociation decreases with an increase in temperature in an aqueous solution, such as formic acid, acetic acid, propionic acid, butyric acid, chloracetic acid, phosphoric acid, oxalic acid, malonic acid and the like. On the other hand, it is also possible to use an acid such as boric acid or carbonic acid whose degree of dissociation increases with temperature rise. Furthermore, the salt obtained by the neutralization of the weak base and the weak acid as described above is also temperature-dependent in the degree of dissociation and can be used as a weakly ionizable substance in the present invention. Whether the degree of dissociation increases or decreases depending on temperature depends on the magnitude relationship between the strength of the acid and the base.

Further, instead of using a weak acid or a weak base alone, a mixed system of a weak acid and a strong base, a mixed system of a weak base and a strong acid, and the like can be used.

Further, as a method for preparing a colloidal polycrystal dispersion in which colloidal crystals are precipitated at a predetermined temperature, temperature change of dielectric constant of the medium can also be used. That is, although the electrostatic interaction between colloidal particles increases with the decrease of the dielectric constant, the dielectric constant of the ordinary liquid decreases with the temperature, so the dielectric constant can be changed by heating to precipitate the colloidal crystals.

The colloidal particles of the colloidal polycrystal dispersion may be silica particles, the dispersion medium may be water, and the weak base may be pyridine and / or a pyridine derivative. With such a colloidal polycrystal dispersion, it is possible to reliably produce large single crystals with few lattice defects and nonuniformities.

Also, even if a strong base is added to the colloidal polycrystal dispersion, colloidal crystals can be precipitated at a predetermined temperature. Although the temperature dependence of the degree of dissociation of the strong base is considered to be low, it is nevertheless possible to precipitate the colloidal crystal even by the addition of the strong base because the dielectric of the colloidal polycrystal dispersion according to the temperature change. It is considered that the change in the rate or the change in the degree of dissociation of the functional group on the surface of the colloidal particle due to the temperature change. Furthermore, even if nothing is added to the colloidal polycrystal dispersion, the colloidal crystal is changed by changing the temperature to change the dielectric constant of the colloidal polycrystal dispersion and the degree of dissociation of the functional group on the surface of the colloidal particle. It can be deposited.

In addition, after the colloidal crystal is grown, it can be solidified by gelation. Thus, solidifying the colloidal crystal by gelation can maintain the structure of the colloidal crystal even when the temperature is returned to a temperature at which the colloidal crystal does not precipitate. In addition, the mechanical strength of the colloidal crystal can be dramatically increased. Furthermore, the gelled colloidal crystal is a material having the unique properties of the gel matrix. For example, when the gelled colloidal crystal is mechanically compressed and deformed, the crystal lattice spacing also changes, so that the material can control the diffraction wavelength. The gelled colloidal crystals swell or shrink in response to the type of liquid, physical or chemical environment such as temperature or pH. Also, when a functional group that specifically binds to a specific molecule is introduced, the volume changes depending on the concentration of the molecular species. By using these properties and measuring the shift of the diffraction wavelength, it becomes possible to sense temperature, pH, various molecular species and so on.

As a method of gelation, a photocurable resin is dispersed in a colloidal polycrystal dispersion liquid, and a colloidal crystal is precipitated, and then light is irradiated to gelate. In this case, as the photocurable gelling agent, it is preferable to select a material that generates less ions. This is because when using a photocurable gelling agent from which ions are generated, the surface potential of the charged colloid dispersed in the colloidal polycrystal dispersion may change to cause a state change of the colloid. Examples of such a photocurable gelling agent with low ion generation include solutions containing a gel monomer, a crosslinking agent, and a photopolymerization initiator. As gel monomers, vinyl monomers such as acrylamide and derivatives thereof, N, N'-methylenebisacrylamide as a crosslinking agent, and as a photopolymerization initiator, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide] and the like. In addition to this, a water-soluble photosensitive resin having an azide-based photosensitive group pendant to polyvinyl alcohol can also be used.

In the method for producing a colloidal crystal according to the present invention, in the recrystallization step, cooling or heating from one end side of the container by the temperature control means is performed to melt the colloidal polycrystal in the colloidal polycrystal dispersion, and then the temperature control means is used. It is also possible to stop the cooling or heating and recrystallize.

According to the test results of the present inventors, it is possible to reliably manufacture a large-size, small lattice defect and non-uniform colloidal crystal even using such a colloidal crystal recrystallization method. Moreover, according to this method, it is not necessary to move the melting region as in the zone melt method, so that the apparatus can be simplified, and the cost of manufacturing the colloidal crystal can be reduced.

The colloidal crystal obtained by the production method of the present invention can be set to a very narrow range of 10 nm or less in the absorption spectrum and the reflection spectrum. In addition, spatial nonuniformity of the diffraction wavelength can also be 0.2% or less. Here, spatial nonuniformity refers to the standard deviation of the spatial distribution of diffraction wavelengths of a colloidal crystal measured by reflection spectroscopy or transmission spectroscopy, divided by the weighted average value of diffraction wavelengths, and expressed as a percentage (Same below).

In the production method of the present invention, the diffraction wavelength is in the range of 400 to 800 nm, the nonuniformity of the diffraction wavelength is 0.2% or less, and the transmittance at the diffraction wavelength is 0 at a thickness of 1 mm. It is not more than 1%, the number of layers in the crystal lattice plane is 3,000 or more, and a colloidal crystal composed of a single crystal having a maximum diameter of 1 cm or more can be obtained.

With such a colloidal crystal, the diffraction wavelength is in the range of 400 to 800 nm, so that visible light can be diffracted. Also, the spatial non-uniformity of the diffraction wavelength is 0.2% or less, and the accuracy of the diffracted wavelength is extremely high. Moreover, since the transmittance at the diffraction wavelength is 0.1% or less, the efficiency of diffraction is also extremely good. Due to these characteristics, the present invention can be applied to the fields of optical communication connectors, optoelectronic devices such as optical amplification, color imaging devices, high-power lasers, cosmetics and accessories as a photonic crystal.

It is a graph which shows the relationship between the pyridine concentration and melting _| fusing point _Tm and freezing point _Tf which were calculated _| required from the melt _| fusion test of the colloid polycrystal dispersion liquid. It is a schematic diagram of the experimental apparatus for calculating | requiring the melting curve of a colloidal polycrystal dispersion liquid. It is a graph which shows the melting curve of a colloidal polycrystal dispersion liquid. It is a schematic diagram of an apparatus used for precipitation of a colloid crystal by a zone melt method. It is a photograph before and behind precipitation of the colloid crystal by a zone melt method. It is a figure which shows the external appearance and crystal size of a colloid crystal at the time of changing the moving speed of a Peltier device. It is a photograph which shows the result of having measured cell surface temperature with an infrared type thermography apparatus at the time of performing single crystallization of the colloid crystal by a zone melt method. It is a photograph after the impurity exclusion test by a zone melt method. It is the graph which measured the fluorescence luminance distribution of the photograph which image | photographed the fluorescence image about the colloid crystal. It is a figure which shows the principle of recrystallization by a zone melt method. FIG. 14 is a schematic view of an apparatus used for the method of producing a colloidal crystal of Example 3. It is a photograph of a colloidal crystal after recrystallization. It is a graph which shows the relationship of the elapsed time and the temperature in each part in the method of stopping a cooling after cooling from one direction, and making a colloidal crystal precipitate. It is a graph which shows the permeation | transmission spectrum of the photograph and the polycrystal area | region of a colloidal crystal, and a recrystallization area | region after performing recrystallization with the pyridine concentration set to 47.5 micromol / L and the volume fraction ((phi)) of a silica colloid being 0.035. It is a graph which shows the relationship between the pyridine concentration in a colloidal polycrystal dispersion liquid, and a half value width. It is a diffraction image obtained by Kossel line analysis of a recrystallized region. It is a photograph of the colloidal crystal gelled in Example 3-3. It is the transmission spectrum of the part to which the zone melting method in Example 3-3 is not applied, and the part to which the zone melting method was applied.

1, C ... quartz cell (container)
2, 12 ... thermocouple 3 ... water tank (temperature control means)
4 ... Automatic X axis stage (moving means)
5: Base 6: Stage 7: Stepping motor 9: Peltier element 10: Convex member 11a, b: Heat insulation member

Particularly preferred as an example of the colloidal polycrystal dispersion used in the present invention is a system in which silica fine particles are dispersed in water. When the silica fine particles are dispersed in water, partially dissociated Si-O of OH weakly acidic silanol groups covering the surface (Si-OH) ^- with the, and the counterions around The called plus ion (H ⁺ ) is distributed. When an ionizable substance such as pyridine is added to this system, the degree of dissociation of the silanol group changes, and the effective surface charge density σ _{e of the} particles changes. Thus, the characteristic that the effective surface charge density σ _e can be controlled relatively easily. Is the merit of silica particles, which can be used to prepare colloidal crystals.

However, the colloidal polycrystal dispersion used in the method for producing a colloidal crystal of the present invention is not limited to the silica-water system, and colloidal particles having a charge derived from a weak acid or weak base on the surface are dispersed in a liquid medium. The addition of a weakly ionizable substance as described above can be applied to other ionic colloid dispersion systems in which the ionized substance is dissociated (ionized) in the liquid medium and the charge on the surface of the colloidal particle can be changed.

That is, as colloidal particles, those having a weak acid on the surface can be used similarly to silica, and for example, titanium oxide fine particles, carboxy-modified latex (latex having carboxyl group on the surface), etc. can be used. Furthermore, as long as it has a weak base on the surface, by adding a weak acid, a function similar to that of silica + pyridine can be expressed, and the corresponding colloidal particles have aluminum oxide or an amino group. Latex etc. can be mentioned. In addition, since the surface of the particles only needs to have the above-mentioned properties, the present invention can be applied to particles whose surface is coated with silica, a titanium oxide layer or the like.

It is also applicable to colloidal systems consisting of globular proteins and clay minerals with both weak acids and weak bases. Furthermore, various types of colloidal acids including various colloidal particles in which various weak acids and weak bases are introduced to the particle surface by surface modification methods such as introducing a weak base to the surface of silica particles using a silane coupling agent having an amino group The present invention is also applicable to crystal dispersions.

With regard to the dispersion medium, a liquid other than water can be exhibited as long as it can exhibit a high dielectric constant such that the dissociative group (charge-imparting group) on the surface of the colloidal particle and the weakly ionized substance (weak acid, weak base, salt) can be dissociated. Are also available. For example, formamides (eg, dimethylformamide) and alcohols (eg, ethylene glycols) can be used. These can be used as they are depending on the combination of the colloidal particles and the weakly ionized substance to be added, but in general, it is preferable to use as a mixture with water.

As a colloidal polycrystal dispersion liquid to which a weak acid or a weak base is added, a commercially available colloidal particle may be dispersed in an appropriate dispersion medium such as water, or a sol-gel method etc. may be used. Since the formation of crystals is inhibited by the presence of a trace amount of salt (ionic impurities), it is preferable to carry out sufficient desalting in preparation of the colloidal dispersion system. For example, in the case of using water, first, purified water is dialyzed until the electric conductivity of the used water becomes approximately equal to the value before use, and then the ion exchange resin (cation And desalting purification by keeping the mixed bed of anion exchange resin in the sample for at least one week.

In addition, attention must be paid to the size of the colloidal particles and their distribution. The particle diameter of the colloidal particles is preferably 600 nm or less, more preferably 300 nm or less. This is because, in the case of a colloidal particle having a large particle diameter such as a particle diameter exceeding 600 nm, it tends to settle due to the influence of gravity. Further, the standard deviation of the particle diameter of the colloidal particles is preferably 15% or less, more preferably 10% or less. If the standard deviation is large, crystals are less likely to form, and even if crystals are formed, lattice defects and inhomogeneity increase, and it is difficult to obtain high quality colloidal crystals.

In the case of a colloidal polydispersion in which colloidal crystals are formed on temperature change by addition of weakly ionizable substances, the electrostatic interaction between the colloidal particles governing crystallization in the charged colloid system is the effective surface of the particles. Not only charge density (σ _e ) but also particle volume fraction (φ) and additive salt concentration (Cs) are influenced. Therefore, the temperature at which crystallization of the colloid occurs and the amount of weakly ionized substance to be added differ depending on φ and Cs of the initial colloidal dispersion system. For example, when pyridine (Py) is added as a weakly ionizable substance, crystallization generally occurs under conditions of higher pyridine concentration as the Cs value is higher when compared under constant temperature and φ conditions.

Generally, a colloidal dispersion system is prepared so that φ (volume fraction of colloid particles) is about 0.01 to 0.05, and Cs (addition salt concentration) is about 2 to 10 μmol / L. Add weakly ionized substance to the For this purpose, the specific gravity of the colloidal particles can be determined by the picometer method or the like, and using this value, the φ value of the colloidal particles of the colloidal dispersion system can be determined by the absolute drying method. Then, a liquid medium such as purified water is added to this colloidal dispersion system and diluted to prepare a dispersion system having a predetermined φ value. The φ value is calculated so as to have a crystal plane spacing in accordance with the desired characteristics of the colloidal crystal. Also, if necessary, an aqueous solution of low molecular weight salt such as NaCl is added to control the Cs value.

In the preparation of the above colloidal polycrystal dispersion, it is necessary to avoid contamination with ionic impurities as much as possible. In this respect, soda lime glass or the like in which basic impurities are eluted in water increases the σ _e value of the particles, so when using a glass container, basic impurities such as quartz glass are eluted in water A non-glass container is preferred. In addition, carbon dioxide in the air dissolves in water to form carbonic acid, so it is desirable to prepare under an atmosphere such as nitrogen. Furthermore, containers and instruments used for crystallization of colloids are used after thoroughly washing with purified water (electrical conductivity: 0.6 μS / cm or less).

The colloidal system prepared as described above can be heated or cooled, the presence or absence of crystals can be confirmed, and the crystallization temperature can be evaluated. For confirmation of crystal formation, X-ray scattering, optical microscopy, spectrophotometry (reflection or transmission spectrum measurement), and the like can be applied in addition to the observation of iridiumescence.

In the method for producing a colloidal crystal of the present invention, crystallization of colloidal particles can be generated thermoreversibly by a simple means of simply heating or cooling the system from the outside. This crystallization can be controlled by changing the concentration of weakly ionizable substances such as pyridine, but the concentration of weakly ionizable substances does not have to be as strict as when adding a strong base such as NaOH. . That is, since the concentration of the dissociated species is very small compared to the concentration of the weakly ionized substance added, the change of the surface charge density (σ _e ) of the colloidal particle with respect to the weakly ionized substance concentration is more gradual than that when the strong base is added. The advantage is that a certain concentration range is acceptable.
In addition, the crystallization temperature can be easily adjusted by changing the concentration of the weakly ionized substance. It has already been confirmed that the silica / water colloid using pyridine can be adjusted in the range of 2 to 60.degree.

Further, in the present invention, since the system can be kept in a closed system, it is possible to prevent contamination by ionic impurities and obtain high-performance colloidal crystals. Thus, the present invention is expected to be applied to a wide range of applications such as optical elements whose light response characteristics can be controlled.

The method for producing a colloidal crystal according to the present invention utilizes a colloidal particle having a charge on the surface, a dispersion medium for dispersing the colloidal particle, and a colloid system containing a weakly ionizable substance whose degree of dissociation changes with temperature change in the dispersion medium. It is possible to externally apply a temperature change to this to generate a colloidal crystal. Such a weakly ionized substance-containing colloid system reversibly crystallizes and changes its physical property due to temperature change, and therefore, it is possible to apply this property to applications other than the production of colloidal crystals.

For example, it becomes possible to develop a novel heat-sensitive material (heat-sensitive paint, temperature sensor, etc.) utilizing the change in physical properties due to temperature change. In addition, if a system is used in which the colloidal system crystallizes by raising the temperature, the viscosity of the system is expected to increase with the temperature. On the other hand, in an ordinary simple liquid, the viscosity generally decreases monotonically as the temperature increases. Application to the improvement of the temperature characteristic of, for example, a liquid (such as oil for a clutch) used in a conventional stress transfer system is also expected by utilizing such a unique viscosity-temperature characteristic.

Hereinafter, the embodiments of the present invention will be described in detail.

<Preparation of Colloidal Polycrystalline Dispersion>
A colloidal polycrystal dispersion was prepared as follows.
Silica colloid particles KE-W10 (diameter 0.11 ± 0.01 μm specific gravity 2.1) manufactured by Nippon Shokubai Co., Ltd. were purified by dialysis using a semipermeable membrane and ion exchange using an ion exchange resin. The silica colloid from which ions were removed in this manner was adjusted to have a volume fraction (φ) = 0.050, and pyridine was added to a predetermined concentration to obtain a colloidal polycrystal dispersion. The colloidal polycrystal dispersion becomes a white turbid solution when shaken vigorously at room temperature, but when left as it is, fine colloidal polycrystals sparkling with glitter and interference color are observed with the naked eye within one minute.

Melting Test of Colloidal Polycrystalline Dispersion
A melt test of colloidal crystals was conducted on the colloidal polycrystal dispersion thus obtained. That is, the colloidal polycrystal dispersion was filled in a quartz cell having a thickness of 1 mm, a width of 1 cm, and a length of 4.5 cm according to the internal method, placed in a thermostat, and the melting point was measured while lowering the overall temperature. It was observed by visual observation whether the melting point was reached. That is, when the colloidal crystal melts, it changes from a colloidal polycrystal state of sparkling glitter and interference color to a clouded molten state through a solid-liquid coexistence state in which sparkling points are scattered. The temperature when transitioning from the molten state to the solid-liquid coexistence state is the melting point T _m , and the temperature when transitioning from the solid-liquid coexistence state to the crystal state is the freezing point T _f, and the melting point T _m and the freezing point T at various pyridine concentrations _f was measured.

As a result, as shown in FIG. 1, T _m and T _f depend on the concentration of added pyridine, and T _m and T _f decrease as the concentration of pyridine increases, and T _m and T _f depend on the amount of addition of pyridine. It turned out that the value of can be controlled.

Furthermore, the melting test shown below was conducted. That is, as shown in FIG. 2, the quartz cell 1 filled with the colloidal polycrystal dispersion is fixed in the horizontal direction, and a large number of thermocouples 2 in the width direction at the top face side in the length direction, etc. Installed at intervals, it was possible to measure the temperature of each part. Then, one end side of the quartz cell 1 is brought into contact with the water tank 3 connected to a cooling water circulation device (not shown) to circulate cold water of a predetermined temperature (0 ° C., 3 ° C., 7 ° C.) The colloidal crystals were melted. The state of melting of the colloidal crystals could be clearly confirmed by the naked eye. That is, before bringing the water tank 3 into contact with the quartz cell 1, the whole cell was a crystal region in which an interference color is observed, but after bringing the water tank 3 into contact with one end of the quartz cell 1, the colloidal crystal It was observed that the melted region in the cloudy state spread from one end to the other end. Furthermore, bright spots were scattered between the melted region and the crystalline region, and a solid-liquid coexisting region considered to be a liquid crystal state was observed. Then, the temperature at the boundary between the melting region and the solid-liquid coexistence region was measured as the melting point T _m , and the temperature at the boundary between the solid-liquid coexistence region and the crystal region as the freezing point T _f .

As a result, a melting curve (L in the figure indicates the distance from the water tank 3) shown in FIG. 3 was obtained. Each T _m value showed good agreement with the calculated value from the T _m value obtained in FIG.

Precipitation of Colloidal Crystals by Zone Melt Method
Example 1-1
In Example 1-1, a large colloidal single crystal was prepared from fine colloidal polycrystals by the zone melt method shown below.
First, silica colloid particles KE-W10 (diameter: 0.11 ± 0.01 μm, specific gravity: 2.1) manufactured by Nippon Shokubai Co., Ltd. were purified by dialysis using a semipermeable membrane and ion exchange using an ion exchange resin. The silica colloid from which ions were removed in this way was adjusted to have a volume fraction (φ) = 0.050, and pyridine was added so as to be 50 μmol / L to obtain a colloidal polycrystal dispersion. In this colloidal polycrystal dispersion, fine colloidal polycrystals were observed with the naked eye when sparkling at room temperature. The colloidal polycrystal dispersion was separately charged in a quartz cell, and after precipitation of fine colloidal polycrystals, it was cooled, and the temperature at which the colloidal crystals melted was measured to be 10 ° C.

A colloidal polycrystal dispersion in which this fine colloidal polycrystal is dispersed is filled in a quartz cell C having a thickness of 1 mm, a width of 1 cm and a length of 4.5 cm as shown in FIG. A quartz cell C was placed on the X-axis stage 4 so as to be parallel to the horizontal plane. The automatic X-axis stage 4 is provided with a rectangular stage 6 on a base 5, and a stepping motor 7 is attached to one end of the base 5. The stage 6 can be moved in the longitudinal direction via a rack-pinion mechanism (not shown) by driving the stepping motor 7. By controlling the stepping motor 7 by a controller (not shown), the stage 6 can be driven at a predetermined speed. It is movable in one direction.
Also, a U-shaped jig 8 is installed so as to straddle the automatic X-axis stage 4 and a Peltier element 9 is attached to the lower center of the jig 8 with the lower side as the cooling side. There is. A thin plate-like convex member 10 made of aluminum is disposed at the center of the lower surface side of the Peltier element 9 so as to protrude downward while in contact with the Peltier element 9. The width direction of the convex member 10 is the same as the width direction of the quartz cell C, and the tip of the convex member 10 is in contact with the quartz cell C. The Peltier device 9 can be cooled so that the lower surface side has a predetermined temperature by supplying power from a power supply (not shown). Further, the

heat insulating members

11a and 11b are provided on both sides facing the convex member 10 with a slight gap therebetween. Further, a thermocouple 12 is attached near the tip of the convex member 10.

When a quartz cell C containing a colloidal polycrystal dispersion was attached to the stage 6 of the automatic X-axis stage 4, it was visually observed that the colloidal crystals were precipitated within 1 minute after the attachment. After the colloidal crystal was thus deposited, power was supplied to the Peltier element 9, and the stepping motor 7 was driven by the control device to move the stage 6 in one direction at a speed of 2 mm / min. Thereby, the convex member 10 in contact with the cooling surface of the Peltier element 9 is cooled, and the portion of the quartz cell C facing the convex member 10 is cooled to a predetermined temperature. Then, by moving the quartz cell C together with the stage 6, the cooled portion of the quartz cell C was moved in one direction at a speed of 2 mm / min.

FIG. 5 shows the state before recrystallization and after recrystallization by the zone melt method. From this photograph, it was found that although many fine polycrystals were observed before recrystallization, the interference color became homogeneous after recrystallization, and single crystallization progressed. Furthermore, the reflection spectrum and absorption spectrum of the colloidal crystal thus obtained were measured by fiber spectroscopy. As a result, the half width is 6.33 nm before recrystallization, but becomes 5.28 nm after recrystallization (diffraction wavelength is 554 nm both before and after crystallization), and the optical characteristics of the crystal are improved by recrystallization. It turned out to do.

The number of layers of the crystal lattice plane of the obtained colloid single crystal was calculated as follows from the Bragg equation. That is, according to the Bragg equation, 2d · sin θ = N · λ / n _r (where d is the distance between the lattice planes, θ is the angle between the incident light and the lattice plane, N is a natural number, λ is the diffraction wavelength, n _r is the sample (Refractive index). In the measurement of Example 1, θ = 90 ° (sin θ = 1), N = 1, n _r = φ n _{silica particles} + (1-φ) n _water (n _{silica particles} = 1.46, n _water = 1 .33). When φ = 0.050, n _r = 1.45, and d = λ / (2 nr) = 191 nm is calculated. Therefore, it was found that the number of crystal lattice planes is about 5200 (layers) in a 1 mm thick crystal, and the number of layers is extremely large.

Moreover, when the difference in the diffraction wavelength according to the place was examined, the fluctuation of the diffraction wavelength was also very slight (1 nm or less), and the spatial nonuniformity was 0.04% in reflection spectrum measurement: 0.05% in transmission spectrum measurement It has been calculated that it has extremely excellent uniformity. Furthermore, it was found that the transmittance at a diffraction wavelength at a thickness of 1 mm was 0.009, and that the grating exhibited excellent performance as a diffraction grating. In addition, it was found that the transmittance at a wavelength slightly deviated from the diffraction wavelength was large, and the transparency was excellent at wavelengths other than the diffraction wavelength.

(Examples 1-2 to 1-4)
In Examples 1-2 to 1-4, the moving speed of the Peltier element 9 is different from that in Example 1-1 (ie, 18 mm / min in Example 1-2 and 30 mm / min in Example 1-3). In Example 1-4, colloidal crystals were prepared at 42 mm / min. Other preparation conditions are the same as in Example 1-1. The results are shown in FIG. From this figure, it was found that the crystal size becomes smaller as the moving velocity ν of the cooled portion (ie, the melting region of the colloidal polycrystal) increases.

Further, in the preparation of the colloidal crystal of Example 1-1 (ie, ν = 2 mm / min), the cell surface temperature on the opposite side to the Peltier element 9 was measured using an infrared thermographic apparatus (TH6300 manufactured by NEC / Avio). . The results are shown in FIG. FIG. 7 (a) shows an image of the temperature distribution every 5 minutes. FIG. 7B is a diagram showing the relationship between the position x (distance from the left end of the cell) on the horizontal line shown in each image of FIG. 7A and the temperature. In FIG. 7 (a), the darkest portion at 15 ° C. or lower is the Peltier element 9, and the portion in contact with this is the melting zone of the colloidal crystal.

Similar surface temperature measurements were also performed for Example 1-4 ((= 42 mm / min), Example 1-3 ((= 30 mm / min) and Example 1-2 (ν = 18 mm / min). . As a result, the temperature of the cell surface opposite to the side in contact with the Peltier element 9 is 23 ° C. in Example 1-4, 22 ° C. in Example 1-3, and 18 ° C. in Example 1-2. The

<Impurity exclusion experiment by zone melt method>
(Example 2-1)
In Example 2-1, fluorescent polystyrene particles were used as the simulated impurities, and the exclusion test of the impurity particles was performed by the zone melt method. The test method is described in detail below.
That is, in a dispersion obtained by adding 50 μmol / L of pyridine to a purified silica colloid (particle size = 100 nm, particle concentration = 5 vol%), fluorescent polystyrene fine particles (particle size = 100 nm) as a model impurity particle concentration = 0.02 vol% Added to be The colloidal polycrystal dispersion prepared in this way was an aggregate of microcrystals of 1 mm or less. The colloidal polycrystal dispersion is placed in a 1 × 1 × 4.5 cm quartz cell, and using the zone melt apparatus used in Example 1-1, the temperature of the tip of the convex member 10 is 3 ° C. at 25 ° C. While controlling the Peltier element 9, zone melt processing was performed by moving about 3 cm leftward from the right end of the cell at a speed of 2 mm / min. The appearance of the colloidal crystal thus obtained is shown in FIG. The portion indicated by the arrow in the figure is the portion subjected to zone melt processing, and it can be seen that the colloidal single crystal is precipitated. A polycrystalline region remained at the left end of the zone melt-treated portion. Furthermore, the result of examining the distribution of fluorescent particles using a fluorescence microscope is shown in FIG. The fluorescence microscope image in (a) (polycrystal area | region) (b) (boundary area | region) and (c) (recrystallized area | region) shown to the upper figure of FIG. 8 is a lower figure of FIG. Clear fluorescence was observed in (a) but hardly observed in (c). From the above results, it was found that fluorescent particles as simulated impurities were excluded from the single crystal part.

(Example 2-2)
In Example 2-2, fluorescent polystyrene fine particles (particle diameter = 100 nm) were added so that the particle concentration was 0.0005 vol%, and the pyridine concentration was 55 μmol / L. The other conditions are the same as in Example 2-1, and the detailed description will be omitted.

About the colloidal crystal thus obtained, fluorescence images were taken at 1 mm intervals, and the fluorescence intensity was measured using image analysis software. The results are shown in FIG. From this figure, it is clear that after zone melt processing, the brightness of the recrystallized region is reduced compared to before zone melt processing, and the brightness has a maximum at the boundary. That is, it was found that the fluorescent polystyrene particles were excluded from the recrystallized portion by zone melt treatment and accumulated at the boundary.

The above results mean that the zone melt method, which has conventionally been used to obtain single crystals of silicon and the like, can also be applied to colloidal crystal systems. That is, since the crystal grain boundary has a melting point lower than that of the inside of the crystal, the colloidal polycrystals are cooled by the zone melt method to melt fine crystal grains, and when heated again for crystallization, the same crystal orientation as the surrounding The crystal with orientation is remodeled and single crystallization proceeds (see FIG. 10). In addition, it is assumed that other crystal defects (for example, vacancies, twin defects, etc.) can be similarly removed by the zone melting method in which melting / recrystallization is performed.

Preparation of Colloidal Crystal by Method of Stopping Cooling after Precipitation from One Direction and Precipitation of Colloidal Crystal>
(Example 3)
In Example 3, a quartz cell filled with a colloidal polycrystal dispersion composed of colloidal polycrystals is cooled from one direction, and then the cooling is stopped and recrystallization is carried out to prepare a giant colloidal single crystal from fine colloidal polycrystals. did.
The volume fraction (φ) of the silica colloid in the colloidal polycrystal dispersion for crystallization was set to 0.035, and the pyridine concentration was set to 50 μmol / L. The other conditions for preparing the colloidal polycrystal dispersion are the same as in Example 1, and the description will be omitted. The colloidal polycrystal dispersion thus obtained is filled in the same quartz cell as in Example 1, and the quartz cell 20 is fixed in the horizontal direction as shown in FIG. It abuts on the central part of the direction, and the temperature of each part is set to be measurable. Then, one end side of the quartz cell 20 is brought into contact with the water tank 22 connected to a cooling water circulation device (not shown) to make it 0 ° C., and the colloidal crystal is melted from one end side to the other end. The colloid crystals were separated again and precipitated. The thermocouple 21 was placed at a distance of 2.5 mm, 7.5 mm, 12.5 mm and 17.5 mm from the water tank 22. Further, the signal from the thermocouple 21 is digitized by the A / D converter 23 and taken into the personal computer 24 as digital data.

When the state of the precipitation of the colloidal crystal was observed with the naked eye, the state of the melting of the colloidal crystal could be clearly confirmed by the naked eye. That is, when the cooling by the water tank 22 is stopped, the melted region of the turbid state in which the colloidal crystal is melted is observed on the side close to the water tank 22, and the colloid crystal is not melted on the side far from the water tank 22, and the interference color is An observed crystalline region was observed.

A photograph of the case where the colloidal crystal is precipitated is shown in FIG. 12, and the temperature of each part is shown in FIG. 13 (mm in FIG. 13 indicates the distance from the water tank 22). As shown in FIG. 12, it was possible to clearly distinguish between a single crystallization region showing a homogeneous interference color in which the colloidal polycrystal melts and recrystallizes, and a region where the colloidal polycrystal remains as it is without melting. In addition, when the reflection spectrum was measured for the recrystallized part and the non-recrystallized part, the center wavelength was 620 nm for both, but the half width was 5.47 nm for the part not recrystallized. On the other hand, in the recrystallized part, it became as small as 4.64 nm, and it turned out that it has excellent optical properties.

In addition, when the transmission spectrum was measured, as shown in FIG. 14, the portion which did not recrystallize was different in spectrum from one place to another, while almost the same spectrum was obtained everywhere in the recrystallisation region. It turned out that it is excellent in homogeneity.

Further, the same test was conducted while changing the concentration of pyridine in the colloidal polycrystal dispersion to 40 μmol / L, 47.5 μmol / L and 50 μmol / L, and the reflection spectra of the polycrystal region and the recrystallization region were measured. As a result, as shown in FIG. 15, the lower the pyridine concentration, the smaller the half width.

In addition, Kossel line analysis of a colloidal recrystallization region prepared using a colloidal polycrystal dispersion liquid with a pyridine concentration of 50 μmol / L was performed. The Kossel line is originally that when X-rays are irradiated to a single crystal substance, characteristic X-rays generated secondarily inside the crystal work as point light sources, and the light is diffracted by various crystal lattice planes. It indicates the characteristic diffraction pattern to be obtained, and analysis of the Kossel line can determine the orientation and lattice structure of the crystal lattice. This method is applied to the above-mentioned colloidal crystal, and the method of Sawada et al. (T. Kanai, T. Sawada, I. Maki, K. Kitamura. Jpn. J. Appl. Phys., Vol. 42, p. L655 (2003) Kossel line analysis was performed according to). Since the lattice spacing of the colloidal crystal is on the order of the wavelength of light, laser light was used instead of X-ray. A light diffusion plate was provided between the sample cell and the laser light source as equivalent to a point light source to obtain conically spread incident light. (A schematic diagram of the Kossel line analysis system is the Supporting Information of A. Toyotama, J. Yamanaka, M. Yonese, T. Sawada, F. Uchida, J. Am. Chem. Soc. Vol. 129, p. 3044 (2007) It is described in). According to this method, of the conical light incident on the colloidal crystal, a portion removed by diffraction is observed as a shadow. FIG. 16 shows a Kossel line photograph of the single crystal thus obtained. It is concluded that the ring pattern in the center is diffraction from the BCC {110} plane oriented parallel to the cell wall, and the pattern around the ring is due to the BCC {200} plane ( A. Toyotama, J. Yamanaka, M. Yonese, T. Sawada, F. Uchida, J. Am. Chem. Soc. Vol. 129, p. 3044 (2007)). As can be seen from this figure, it was supported that a well-oriented single crystal was formed.

<Gelation of colloidal crystals>
(Examples 3-1 to 3-3)
Colloidal crystals prepared by the above method are known methods (Japanese Patent Application No. 2004-375594: Gel-immobilized colloidal crystals (Inventor: Ryohei Yamanaka, Masako Murai, Koji Yamada, Hiroshi Ozaki, Fumio Uchida, Tsutomu Sawada, Akiko Toyotama) , Ito Kensaku, Higuchi Yoshihiro, Hira Hirohito (Japanese Patent Application No. 2004-375594) Applicant: The Japan Aerospace Exploration Agency, Fuji Chemical Co., Ltd.

That is, first, N-methylol acrylamide (hereinafter referred to as "N-MAM"), N, N'-methylenebisacrylamide (hereinafter referred to as "Bis"), and 2,2'-azobis [2-methyl-N- (2) Preparation of silica colloidal polycrystal dispersion prepared by mixing —hydroxyethyl) -propionamide] (hereinafter referred to as “PA”), silica colloid dispersion and pyridine in a predetermined ratio. Here, Bis plays a role as a crosslinking agent, and PA plays a role as a photopolymerization initiator. The composition of the silica colloidal polycrystal dispersion is 0.05 volume fraction (φ) of silica colloid, 42.5 μmol / L of pyridine concentration, 5 mmol / L of Bis, 50 μg / ml of PA,
The N-MAM was 195 to 390 mmol / L (ie, Example 3-1 is 195 mmol / L, Example 3-2 is mmol / L, and Example 3-3 is 390 mmol / L).

The silica colloidal polycrystal dispersion thus obtained is put into the cell used in Example 1-1, a colloidal single crystal is obtained by zone melt method in a dark room, and the colloidal single crystal is further irradiated with ultraviolet light to obtain N-MAM. Polymerized.
As a result, as shown in Table 1, it was found that the higher the concentration of N-MAM, the harder the gel state (in the table, ○ indicates a hard gel state, Δ indicates a soft gel state, and x indicates a flow state) To indicate no gelation).

A photograph of the gelled colloidal crystals of Example 3-3 is shown in FIG. Here, it is between 15 mm from the right end to the left that the recrystallization of the colloidal polycrystal is performed by the zone melt method, and an interference color consisting of substantially a single color was observed between them. On the other hand, in the portion where the recrystallization of the colloidal polycrystal by the zone melt method was not performed, the colloidal polycrystal consisting of various colors was recognized. Furthermore, when the transmission spectrum of the gelled colloidal crystal thus obtained was measured, as shown in FIG. 18, in the measurement result (a) of the portion to which the zone melt method is not applied, the spectrum largely differs depending on the measurement location On the other hand, in the measurement result (b) of the part where the zone melt method is applied, an almost uniform spectrum is obtained, and by the application of the zone melt method, it is found that single crystallization of the colloidal crystal is progressing The

The present invention is not limited to the description of the embodiments of the invention. Various modifications are also included in the present invention as long as those skilled in the art can easily conceive of the claims without departing from the scope of the claims.

Claims

Preparing a colloidal polycrystal dispersion in which the colloidal polycrystal melts at a predetermined temperature;
Storing the colloidal polycrystal dispersion in a container;
After setting the temperature of a part or all of the region of the colloidal polycrystal dispersion in the container to a temperature at which the colloidal crystal does not precipitate, the colloidal polycrystal is recrystallized by changing it again to the temperature at which the colloidal crystal precipitates. A recrystallization process,
A method of producing a colloidal crystal, comprising:
In the recrystallization step, a temperature control means sets a part of the colloidal polycrystal dispersion to a temperature at which the colloidal crystal melts to form a melting region, and recrystallizing it by a zone melting method in which the melting region is moved. The method for producing a colloidal crystal according to claim 1, characterized in that
3. A method of producing a colloidal crystal according to claim 2, wherein the movement of the melting region is performed by a moving means which enables relative movement between the temperature control means and the container.
The method for producing a colloidal crystal according to claim 1 or 3, wherein the colloidal polycrystal dispersion is filled between two walls facing in a substantially parallel manner in the storing step.
5. The colloidal polycrystal dispersion liquid is added with a weak acid or a weak base whose degree of dissociation changes with temperature change, and colloidal crystals are precipitated by change of pH due to temperature change. The manufacturing method of the colloid crystal of 1st term.
The colloid according to any one of claims 1 to 4, wherein the colloidal particles of the colloidal polycrystalline dispersion are silica particles, the dispersion medium is water, and the weak base is pyridine and / or a pyridine derivative. How to make crystals.
The method for producing a colloidal crystal according to any one of claims 1 to 6, wherein the colloidal crystal is grown and solidified by gelation.
In the recrystallization step, after cooling or heating from one end side of the container by the temperature control means to melt the colloidal polycrystal in the colloidal polycrystal dispersion, cooling or heating by the temperature control means is stopped and recrystallization is carried out The method for producing a colloidal crystal according to claim 1, characterized in that
A colloidal crystal obtained by the method for producing a colloidal crystal according to any one of claims 1 to 8.
10. The colloidal crystal according to claim 9, wherein the half width in the absorption spectrum and the reflection spectrum is 10 nm or less.
11. The colloidal crystal according to claim 9, wherein the spatial non-uniformity of the diffraction wavelength is 0.2% or less.
The spatial nonuniformity of the diffraction wavelength is 0.2% or less, the transmittance at the diffraction wavelength is 0.1% or less at a thickness of 1 mm, the number of layers of crystal lattice planes is 3,000 or more, and the maximum Colloidal crystal according to any one of claims 9 to 11, characterized in that it consists of a single crystal having a diameter of 1 cm or more.